EP3852125A1 - Triggerable fuse for low voltage applications - Google Patents

Abstract

The invention relates to a triggerable fuse for low-voltage applications for the protection of devices that can be connected to a supply network, in particular overvoltage protection devices, consisting of at least one fusible link located between two contacts and arranged in a housing as well as with a trigger device for the controlled disconnection of the fusible link in the event of malfunctions or overload states of the respective affiliated facility. An extinguishing agent is installed in the housing. The at least one fusible conductor has a large number of known electrical bottlenecks, which are designed for the nominal load of the respective fuse. At least one further, additional geometric constriction is provided which, when subjected to tension, can be separated by tearing as a function of the trigger unit.

Description

The invention relates to a triggerable fuse for low-voltage applications for the protection of devices that can be connected to a supply network, in particular overvoltage protection devices, consisting of at least one fusible link located between two contacts and arranged in a housing as well as with a trigger device for the controlled disconnection of the fusible link in the event of malfunctions or overload states of the respective connected device, wherein an extinguishing agent is introduced into the housing.

Conventional fuses are used in large numbers and in many applications to ensure overcurrent or short-circuit protection for cables and lines, but also for connected equipment.

In addition, fuses are used as backup protection for surge arresters in the so-called shunt branch. A corresponding fuse must guarantee protection in the event of a short circuit.

Due to the increasing use and integration of regenerative energy sources in supply sets, increasingly volatile short-circuit values occur at the installation locations of the equipment, depending on the feed-in situation. This can have the consequence that the required melting or switch-off integrals of the fuses have to be varied over a wide range. Under certain circumstances, the selected fuse can no longer guarantee protection under all conceivable feed-in conditions. In principle, the use of circuit breakers with tripping characteristics is an alternative here, but these switches are significantly more expensive than fuses and so, for reasons of cost, are not suitable for all applications.

The special properties of a fuse basically allow only very few design options with regard to a variation or setting of the protection area of the fuse.

In order to be able to adapt and expand the area of application of fuses, it has already been proposed to cut through the conductor of an electrical fuse element with the aid of a pyrotechnically operated separating device. the DE 42 11 079 A1 shows such a solution in which a pyrotechnic charge is ignited when the current flowing through the current conductor of the fuse and detected by a current detection device has a strength that is greater than a predeterminable threshold value.

the DE 10 2008 047 256 A1 discloses a high-voltage fuse with a controllable drive for a shear bar, which destroys several bottlenecks. The control can be carried out from a separate control depending on the fault current.

the DE 10 2014 215 279 A1 discloses a fuse for a device to be protected which is connected in series with the fuse.

With regard to the dimensioning of fuses, the DE 10 2014 215 279 A1 on the melting integral I ² t. Accordingly, the melting of a fusible conductor is determined by its material and geometric properties, so that, depending on the material and / or geometry of the fusible conductor, a respective amount of heat Q is necessary for the evaporation of the fusible conductor.

Special requirements apply in the event that the device to be protected by the fuse is an overvoltage protection device, because this should allow high currents to pass briefly without triggering the fuse, but at the same time also in the case of low-duration spring currents, such as in the event of damage the overvoltage protection device or as a line follow current, switch off early. The first of the requirements mentioned often leads to high rated current values for the fuse. The second of the requirements mentioned can only be sensibly implemented with low nominal current values.

Taking this problem into account, the DE 10 2014 215 279 A1 to a further development of a fuse in such a way that additional contacts are provided, one of the additional contacts representing a trigger contact in order to cause the fusible conductor to melt directly or indirectly by initiating a short circuit. In addition, the fusible conductor can have a predetermined breaking point in the area of one of the further contacts. In one embodiment, the fusible conductor is surrounded at least in sections with an extinguishing medium, in particular with sand.

Regarding the state of the art, refer to the CH 410137 A , the U.S. 2,400,408 A and the WO 2014/158328 A1 referenced.

From the above, it is the object of the invention to provide a further developed triggerable fuse for low-voltage applications for the protection of devices that can be connected to a supply network, in particular overvoltage protection devices, the fuse in addition to the melting integral value based on the fuse nominal value when required and depending on the expected currents, in particular Short-circuit currents, can be triggered in a targeted manner. A known destruction of the fusible conductor by the action of mechanical forces should be used.

The triggering, i.e. the control to disconnect the fuse element in the event of a malfunction, should either be taken over by a higher-level control unit and, in the event that the fuse is integrated as backup protection in overvoltage protection devices, should be taken over by the surge protection device. The triggerable fuse should also be able to trigger on the basis of measured network impedance values.

The structure of the fuse to be created should be inexpensive, the fuse should have a high switching capacity and a small design. By specifying values for the formation of additional bottlenecks, the possibility of a specifically adjustable fuse protection characteristic can be implemented.

The object of the invention is achieved by the features of the independent claims, the subclaims comprising at least useful configurations and developments.

Accordingly, to achieve the object, use is made of a triggerable fuse which is particularly suitable for low-voltage applications for protecting devices that can be connected to a supply network, in particular overvoltage protection devices. The fuse consists of at least one fusible link located between two contacts and arranged in a housing. Furthermore, a trigger device is provided for the controlled disconnection of the fusible conductor in the event of malfunctions or overload states of the connected device, an extinguishing agent being introduced into the housing.

The fuse according to the invention has at least one fusible conductor with several bottlenecks in series, which ensures the passive function of a conventional electrical NH fuse. In addition, the fuse has at least one additional, special bottleneck per fusible link, which does not impair the passive function of the fuse and which can be activated by triggering independently of the current load. This special narrow point is destroyed by mechanical tearing, cutting, punching or punching out or severing a solder connection.

According to one concept of the invention, an area free of extinguishing agent is formed in the housing in such a way that the at least one fusible conductor is exposed in at least one section.

A mechanical separating element can be introduced into the extinguishing agent-free area via an access in the housing in order to mechanically destroy the at least one fusible conductor independently of its melting integral as a function of the trigger device.

In one embodiment of the invention, the separating element is designed as a blade or cutting edge.

The separating element itself can be driven in the direction of the fusible conductor by a bridge igniter.

The mechanical energy for moving the separating element can also be provided by a shape memory alloy or other shape or volume changing media.

The trigger device has a detection and evaluation unit as well as a control for the exemplary bridge detonator and a power supply and has at least one control input.

The detection and evaluation device can interrupt the passive characteristic of the fuse element at any point in time, approx.> 10 ms. Only the area of adiabatic melting remains unaffected. The associated I ² t value is coordinated in a known manner with the consumer to be protected via the fusible conductor dimensioning.

The solution according to the invention also enables the interruption of very small currents far below the passive nominal current strength of the fusible conductor and likewise a current-free interruption. In this way, an interruption can also take place independently of the current flow, for example when there is a measured change in impedance.

Due to the continuous measurement and when designed as a learning system, the evaluation and acquisition unit can take into account changes in the network when determining the current protection characteristic. This is advantageous in the case of a changing number of consumers or a changing network output by energy producers.

Known basic functions for triggering such as current, voltage, their increases or also their time-dependent behavior, but also external control signals can be used to control the trigger function in addition to the impedance evaluation. When protecting surge protection devices, voltage time areas and, in combination with a current assessment, also time developments in power or energy consumption can be used as trigger criteria.

Criteria such as pressure, temperature, light, magnetic fields, electrical fields or the like can be fed in via additional sensors at additional inputs and taken into account.

As stated, the triggerable fuse according to the invention is particularly suitable as an arrester backup fuse for series connection with surge arresters in the low-voltage area of application.

Here, the fuse according to the invention is designed in particular for use with spark gaps and can be designed in accordance with these special features. In principle, the proposed principle is suitable for both direct voltage and alternating voltage applications and also allows use, for example, in the series branch.

Due to its small design, the controllable fuse can be used in a common housing of an overvoltage protection device in series with a spark gap or a varistor.

The fuse protects the overvoltage protection device against, during or, if necessary, after an overload and disconnects it from the mains.

According to a further basic idea of the teaching of the invention, a triggerable fuse is proposed which aims at a defined mechanical cutting of a special, additional constriction of a fuse fusible conductor after activation of a trigger.

According to the invention, there is a constructive coordination of the additional bottleneck with existing passive flow bottlenecks, that is to say classic safety bottlenecks. Quartz sand, for example, is suitable as an extinguishing medium, especially with high switching capacities.

The variant described below solves the problem of creating a fuse which combines the advantages of a classic current-limiting fuse with those of an activatable, quasi-intelligent fuse with only one cutting blade, with a small size and a simple activator. With passive function, the fuse does not lead to an increase in the protection level of the downstream arrester and, when activated, does not generate any voltage above the specified protection level of the respective connected overvoltage protection device.

The solution in this regard is based on one or more parallel fuse-links which are arranged within an extinguishing medium.

The fusible conductors have several conventional electrical, that is, current constrictions in series, the number of which corresponds to the usual design for the corresponding nominal voltage of the fuse.

Corresponding to known NH fuses, the fusible conductors extend predominantly in a straight line axially through the fuse body. The structure and mode of operation of such a fuse and the bottlenecks correspond to those of conventional fuses in the case of high short-circuit currents or virtual melting times of approx. <10 ms.

The at least one fusible conductor preferably has at least one further special mechanical constriction between the usual current constrictions mentioned, which can be severed by at least one actuator and a cutting blade or a similar means.

The cutting blade as a separating element is preferably made of an insulating material or provided with an insulating coating. This insulating cutting blade leads to an extension of the separating distance between the interrupted fusible conductor. The resulting isolating distance is able to achieve a dielectric strength of at least 2.5 kV, preferably 4-6 kV.

The additional bottleneck according to the invention according to further embodiments of the invention differs from known, customary bottlenecks by the measures described below.

The geometric or mechanical additional constriction has a residual cross section which is higher than that of the usual constrictions. The melting integral ^{value (I 2} t value) of the bottleneck is dimensioned in such a way that it is equal to or slightly higher than the switch-off integral of the fuse. This design ensures that the bottleneck does not respond to short-circuit currents.

However, the area of the additional constriction is available for extending the arcs.

The geometric constriction and the cutting blade are located in an area without an extinguishing medium.

This area is preferably separated on both sides with thin webs from the areas with extinguishing medium and the electrical constrictions.

The width of this area is essentially limited to the width of the blade and twice the thickness of the fuse element.

The fusible conductor (s) are / are guided through the insulating web in such a way that preferably no further seal is necessary for the separation area in order to prevent the penetration of an extinguishing medium, for example quartz sand.

The insulating bars can be made of ceramic, vulcanized fiber or also of polymers with or without gas release (POM). The wall thickness is preferably <1 mm.

The width of the cutting blade is preferably greater than the width of the fusible conductor, but at least wider than the additional mechanical constriction.

The blade has a stroke that goes beyond the expansion range of the fusible conductor when it is cut. The distance of the shortest connection between a currentless cut fusible link is ≥ 4 mm. If the arc is switched off, the distance is lengthened by the fusible conductor burn-off. Measures to extend the sliding distance can be provided on the blade. The blade can form an insulating gap with a fixed or deformable counterpart.

With active shutdown, the arc can extend very quickly from the cutting area to the area with extinguishing agent. The pressure development and thus the load on the housing in the cutting area is therefore low. With passive function, the high extinguishing capacity is guaranteed by the constrictions in the two areas with extinguishing agent, for example compacted quartz sand.

The material of the additional constriction in the cutting area is available for an extension of the arc. The choice of material for the blade and the insulation webs or web walls enables comparatively good arc cooling to be achieved in this area as well.

Due to the space-saving design and the low impact on the passive safety behavior, small sizes can be realized. The fusible conductor routing and the impedance do not differ from conventional fuses, which means that the voltage drop in the case of impulse currents can be limited. Due to the passive behavior of the additional bottleneck in the event of a short circuit, the The voltage level of the fuse can be limited and it is possible to maintain the protection level of the arrester.

The possibility of quickly lengthening the arc when cutting only a narrow point in the area with compressed extinguishing agent or so-called "stone sand" means that the fuse can also be activated in the event of high short-circuit currents, which ensures both passive and active functionality.

The above allows the fuse to be activated even at high currents with virtual melting times of <10 ms if only one bottleneck is separated. This means that the fuse can be interrupted practically in the de-energized state, with small currents far below the nominal current strength and even with high fault currents in the kA range after a short time. Almost any time / current characteristic can also be implemented according to the respective requirements.

In an embodiment variant with several fusible conductors, there is the possibility of separating the fusible conductors simultaneously with greater expenditure of force or one after the other with less expenditure of force with a single actuator. The direction of movement can be straight or else circular or eccentric. Likewise, the blades of this type of movement can be designed differently accordingly.

Alternatively, it is possible to separate the fusible conductors with one blade and one actuator each. This also allows counter-rotating or overlapping movement of the blade, with the blades simultaneously being able to serve to form a gap.

In order to implement a quick shutdown if required, a suitable actuator is implemented along with rapid error detection.

In order to avoid explosive-relevant ignition devices or gas generators, it is proposed according to the invention to use a simple igniter, that is to say a so-called bridge igniter, without its own explosive force. In order to still achieve a sufficient force, the pressure wave that occurs during ignition is like a piston / The cylinder principle is used to cut the mechanical or geometric constriction of the fusible conductor (s).

For this purpose, for example, the blade shaft itself can be guided in the piston or connected to the piston or attached to a projectile guided in the piston.

In this respect, the blade can be arranged very close to the fusible conductor. However, it is also possible to select a distance to increase the impulse of the blade if there is sufficient space or if the drive is located outside. Piston but also blade can preferably also be guided. The projectile mentioned sits loosely in the piston. In the piston cavity there is an igniter or bridge igniter, which fills the piston cavity. The cavity is sealed off from the projectile over a distance in the direction of movement which corresponds at least to the movement path up to the severing of the fusible conductor or conductors. This ensures that the seal to the projectile in the piston is only broken after the narrow point has been severed.

As is customary with passive fuses, the fuse fusible conductors are preferably rigidly attached to the fuse housing with a lower cap and an end cap. The separation of the cutting area on both sides from the extinguishing agent area serves as an additional guide for the fusible conductors in the narrow cutting area.

The guide in the feedthroughs of the partitioning plates is designed in such a way that the fusible conductor or conductors, when positioned transversely to the blade, may deform slightly in the direction of the blade movement when the blade hits. It has been shown that this slight deformation requires less effort than a rigid fusible conductor guide. When the fusible conductors are separated, they are bent on both sides between the partition and the blade. Alternatively, punching out is also possible with the appropriate blade design and the necessary forces.

The force effect of the actuator is essentially based on the thermal expansion of the gas surrounding the bridge igniter. This minimally heated amount of gas can easily relax after opening the piston within a very small volume, i.e. possibly directly in the cutting area, so that no reinforcement of the fuse housing, the caps or ventilation or the like has to be provided.

If longer switch-off times are sufficient in the protection concept for the overvoltage protection device or the connected loads, actuators with slower reaction times can also be used. For example, shape memory alloys or other volume-changing materials are conceivable here. The highest requirements for a coordination between the force required for cutting or severing a bottleneck are tied to the required pulse current carrying capacity, at which no separation of the fuse element should be effected.

The loads with arresters based on varistors are lower than with lightning surge arresters based on spark gaps. In general, a maximum load of 100 kA 10/350 µs is assumed for lightning arresters. In conventional AC networks, this means a load of 25 kA 10/350 µs for the individual spark gap. The fuse element of a fuse should meet the above requirement for the application described. This applies to both the usual electrical bottlenecks and the additional mechanical or geometric bottleneck described.

In the case of a conventional NH fuse, this requirement corresponds approximately to a fuse with a nominal current of 315 A. With regard to the nominal voltage of the fuse, a voltage in the range of the line-to-line voltage of the network in which the arrester is used is often selected. The fuse should therefore be suitable for a voltage of 400 volts in a conventional 230/400 volt network. In the event of a shutdown, the arrester backup fuse does not generate an arc voltage that is above the protection level of the arrester. When designing the bottlenecks of NH fuses, a voltage of approx. 300 volts can be expected for each bottleneck. These requirements result in a number of a minimum of three and a maximum of five common known bottlenecks for such a fuse, as a result of which a common protection level of approx. 1.5 kV is generally not exceeded.

Another variant of the solution according to the invention is based on a controllable fuse, in particular for use as an arrester backup fuse, in which case a defined rupture of a fuse is achieved in this variant Fuse fuse using a special, additional bottleneck.

This approach is therefore aimed at a space-saving and inexpensive embodiment of a triggerable fuse, which is based on the defined tearing of a special additional constriction of a fuse fusible conductor in the extinguishing medium after activation of a trigger. The other properties of an otherwise passively fully functional fuse are not impaired. The special features of this approach are the simplicity of the trigger and the coordination of the additional, geometric bottleneck with the classic, well-known safety bottlenecks.

When tensile forces are exerted on one or more fusible conductors, all existing bottlenecks, i.e. the entire fusible conductor strip and the fastening of the strip, are stretched. With fusible conductors of 5-8 cm length, the stretching length can easily be several millimeters to the point of tearing, especially with copper fusible conductors.

If a separation distance of approx. 3 mm is to be created, the necessary stroke can already be well over 10 mm, which leads to an undesirable enlargement of such a component.

In order to limit the expansion, it is possible to partially fix the fuse element against the housing or the extinguishing agent (sand). Alternatively, there is the possibility of partially solidifying the extinguishing agent.

In contrast to the measures explained above, according to the teaching according to the invention, the expansion on the fusible conductor takes place predominantly at an additional mechanical, that is to say geometric, predetermined breaking point.

The entire extension is therefore only slightly above the necessary elongation at break of the predetermined breaking point and the desired separation distance.

The additional mechanical predetermined breaking point, also referred to as a tension point, must be coordinated and dimensioned in conjunction with the known electrical narrow points.

So that the mechanical constriction has a significantly lower tensile strength, the cross section of this is smaller than that of the electrically relevant one Bottlenecks. However, it must be ensured that despite the smaller cross-section with the same current load, the mechanical bottleneck does not respond before the electrical bottlenecks with all current loads, including transient loads, but with a time delay or with higher loads.

The relevant embodiment of the invention is therefore based on one or more parallel fuse fusible conductors in an extinguishing medium. The fusible conductors have several conventional bottlenecks in series, the number of which corresponds to a conventional design for the corresponding rated voltage of the fuse.

According to conventional NH fuses, the fusible conductors extend predominantly in a straight line axially through the fuse body. The fusible conductor or conductors preferably have at least one further, special constriction between the known constrictions mentioned, which can be torn by an actuator.

The actuator used also requires a defined extension of the interrupted fusible conductor. The resulting overall isolating distance achieves a dielectric strength of at least 2.5 kV.

The additional bottleneck differs from the usual bottlenecks in the following features.

The additional, mechanical or geometric constriction has a residual cross-section which is significantly smaller than that of the usual constrictions. The melting integral value of the bottleneck is the same or even greater than that of the usual known bottlenecks during the period of transient pulse current loads, in particular the current pulse shape 8/20 microseconds and 10/350 microseconds.

In addition, the mechanical strength compared to the direction of force of the actuator is significantly smaller than the mechanical strength of the other, known constrictions.

In this respect, the force of the actuator acts almost only on the additional constriction according to the invention. The elongation of the usual, known constrictions as a result of the force applied by the actuator is negligible.

The mechanical bottleneck is designed in relation to the electrical bottleneck in such a way that it generally does not respond to line-frequency loads. However, the area of the bottleneck is available for the extension of the arcs from the normal bottlenecks.

The dimensions of the mechanical constriction are therefore significantly smaller than the known constrictions. In the case of ribbon-shaped fusible conductors, the bottleneck is designed in such a way that an uneven current distribution can be avoided as far as possible, even with steep increases in current. For this purpose, the narrow point is ideally designed as a tapering of the strip on both sides over the entire width with a length <500 µm, optimally <100 µm. In such a configuration with customary punchings or continuous recesses, these are implemented in such a way that the recesses are similarly short and the width of the recesses does not exceed the length by more than twice.

In principle, other design variants are also possible. The aim of the proposed measures is a current density distribution that is as uniform as possible in the fusible conductor and the constrictions, even with a pulsed current load, with very good and almost distortion-free heat dissipation from the area of the geometrical constriction.

The above ensures a lower temperature rise within the mechanical constriction with a smaller cross-section than in the usual electrical constriction with a larger cross-section, even with rapid current pulse loads of up to <1 ms.

• Fig. 1 ein Blockschaltbild einer Grundanordnung, bestehend aus Erfassungs- und Bewertungseinheit, Ansteuerung, Energieversorgung und triggerbarer Sicherung;
• Fig. 2 einen beispielhaften Aufbau einer triggerbaren Sicherung im Schnitt;
• Fig. 3 eine beispielhafte Zeit/Strom-Kennlinie einer erfindungsgemäßen triggerbaren Sicherung;
• Fig. 4 einen beispielhaften Schmelzleiter für eine Kapselsicherung mit Engstellen, welche zur Erzielung kurzer Schmelzzeiten bei kleinen Überströmen länger als bekannte, übliche Engstellen ausgestaltet sind;
• Fig. 5 eine Bauform mit nicht geradlinigem Schmelzleiter, sondern mit einer winkeligen Führung des Schmelzleiters mit den Anschlüssen A und B;
• Fig. 6 eine prinzipielle Anordnung mit zwei Schmelzleitern und gegenläufigen Klingen mit jeweils einem Aktor;
• Fig. 7 einen Teilbereich der Anordnung gemäß Fig. 2 nach einer Trennung ohne Lichtbogeneinwirkung;
• Fig. 8a eine Anordnung, bei welcher die Schmelzleiter gleichzeitig und quer geschnitten werden;
• Fig. 8b eine Darstellung des gleichzeitigen Schneidens der Schmelzleiter mit vertikaler Ausrichtung zum Schmelzleiter;
• Fig. 9 ein Schneidelement mit zwei versetzten Klingen im Querschnitt, welches das Schneiden von zwei Schmelzleitern quer mit kurzem Hubweg ermöglicht;
• Fig. 10 jeweils Klinge und Aktor zum Schneiden eines Schmelzleiters mit kurzen Hubwegen und gegenläufiger Bewegung der Klingen;
• Fig. 11 ein Schneidelement mit zwei Klingen und rotatorischer Bewegung, welche durch eine entsprechende Führung und nur einem Aktor erzwungen werden kann;
• Fig. 12 eine Ausführungsform, bei welcher ein weiterer Sicherungsschmelzleiter, welcher beispielsweise drahtförmig ausgeführt werden kann, durch die Trenneinrichtung nicht unterbrochen wird;
• Fig. 13 eine Alternative zu einem Draht mit einem Schmelzleiter auf einem Träger;
• Fig. 14 eine Schneidanordnung parallel zu einer Hörnerfunkenstrecke, welche mit einem Sicherungsdraht geringer Nennstromstärke kurzgeschlossen ist, und wobei beim Durchtrennen des Hauptschmelzleiters der Strom auf den Sicherungsdraht kommutiert, welcher die Hörnerfunkenstrecke zündet, die dann den Strom in einer Löschkammer löscht;
• Fig. 15 eine Weiterbildung einer Schneid- und Trennklinge;
• Fig. 16 eine Anordnung mit einem Aktor mit kurzem, jedoch variablen Hubweg;
• Fig. 17 einen Schmelzleiter mit bekannten Engstellen in Form von länglichen Ausnehmungen, wobei zwischen den bekannten Engstellen ein Bereich mit unvermindertem Querschnitt vorgesehen ist und innerhalb dieses Bereiches eine Zusatzengstelle in Form mehrerer rautenförmiger Ausnehmungen mit kurzer Gesamtlänge ausgeführt ist;
• Fig. 18 einen Schmelzleiter für eine Kapselsicherung mit Engstellen, welche zur Erzielung kurzer Schmelzzeiten bei kleinen Überströmen anders gestaltet sind als übliche, bekannte Engstellen;
• Fig. 19 eine Ausführungsform, bei welcher zwischen üblichen, bekannten Engstellen die erfindungsgemäße zusätzliche mechanische Engstelle 4 eingebracht ist;
• Fig. 20a-c verschiedene Gestaltungsvarianten der zusätzlichen, erfindungsgemäßen mechanischen Engstelle;
• Fig. 21a und b ein beispielhafter Aufbau einer NH-Sicherung in Kapselbauform (ausschnittsweise) mit A im Normalzustand und B ausgelöst;
• Fig. 22a und b eine Ausführungsform für eine Verwendung von Formgedächtnislegierungen mit spezieller Nutzung der Zugkraft;
• Fig. 23 eine Ausführungsform, bei der die Zugkraft an einer Lotstelle wirkt, welche beispielsweise durch eine Reaktionsfolie mit exothermer Reaktion innerhalb kürzester Zeit, das heißt im Millisekunden-Bereich, gelöst werden kann.

The invention will be explained in more detail below on the basis of exemplary embodiments and with the aid of figures. Here show:

• Fig. 1 a block diagram of a basic arrangement, consisting of a detection and evaluation unit, control, power supply and triggerable fuse;
• Fig. 2 an exemplary structure of a triggerable fuse in section;
• Fig. 3 an exemplary time / current characteristic curve of a triggerable fuse according to the invention;
• Fig. 4 an exemplary fusible conductor for a capsule fuse with constrictions, which are designed to achieve short melting times with small overcurrents longer than known, usual constrictions;
• Fig. 5 a design with not a straight fusible conductor, but with an angled guide of the fusible conductor with the connections A and B;
• Fig. 6 a basic arrangement with two fusible conductors and opposing blades, each with an actuator;
• Fig. 7 a portion of the arrangement according to Fig. 2 after a separation without the effect of an arc;
• Figure 8a an arrangement in which the fusible conductors are cut simultaneously and transversely;
• Figure 8b a representation of the simultaneous cutting of the fusible conductor with a vertical alignment to the fusible conductor;
• Fig. 9 a cutting element with two offset blades in cross-section, which enables two fusible conductors to be cut transversely with a short stroke;
• Fig. 10 Blade and actuator for cutting a fusible conductor with short stroke paths and opposite movement of the blades;
• Fig. 11 a cutting element with two blades and a rotary movement, which can be forced by a corresponding guide and only one actuator;
• Fig. 12 an embodiment in which a further fuse fusible conductor, which can be designed in the form of a wire, for example, is not interrupted by the separating device;
• Fig. 13 an alternative to a wire with a fuse element on a carrier;
• Fig. 14 a cutting arrangement parallel to a horn spark gap, which is short-circuited with a fuse wire of low nominal current strength, and wherein when cutting through the main fusible conductor, the current on the Commutation fuse wire, which ignites the horn gap, which then extinguishes the current in an arcing chamber;
• Fig. 15 a further development of a cutting and separating blade;
• Fig. 16 an arrangement with an actuator with a short, but variable stroke;
• Fig. 17 a fusible link with known constrictions in the form of elongated recesses, an area with an undiminished cross-section being provided between the known constrictions and an additional constriction in the form of several diamond-shaped recesses with a short overall length being implemented within this area;
• Fig. 18 a fusible link for a capsule fuse with constrictions, which are designed differently than usual, known constrictions in order to achieve short melting times with small overcurrents;
• Fig. 19 an embodiment in which the additional mechanical constriction 4 according to the invention is introduced between conventional, known constrictions;
• Figures 20a-c different design variants of the additional mechanical constriction according to the invention;
• Figure 21a and b an exemplary structure of a NH fuse in capsule design (excerpts) with A in the normal state and B triggered;
• Figure 22a and b an embodiment for a use of shape memory alloys with special use of the tensile force;
• Fig. 23 an embodiment in which the tensile force acts at a soldering point, which can be released within a very short time, that is to say in the millisecond range, for example by a reaction film with an exothermic reaction.

the Fig. 1 shows a basic arrangement of an embodiment according to the invention, which consists of a detection and evaluation unit 1, a control 2, a power supply 3 and the triggerable, controllable fuse 4.

The control unit 2 has an additional external control input 5.

The acquisition and evaluation unit 1 has several measurement inputs 8 and an input for current measurement 6 and for voltage measurement 7.

Additional sensors can be connected to inputs 8.

It is also possible to provide a communication input for external measuring devices.

The signal output to the fuse 4 can be wired or wireless if the ignition device (bridge igniter) is supplied separately.

the Fig. 2 shows an exemplary structure of a triggerable fuse with cutting element 13 in section.

In relation to the fuse, this representation corresponds to the classic structure of known NH fuses with an extinguishing agent in the form of quartz sand and an additional area for activating a bridge igniter 14.

The fuse 4 according to the invention has two connection caps 9, two fusible conductors 10, two areas 11 with an extinguishing agent, for example quartz sand, and an area 12 free of extinguishing agent. In the area 12 free of extinguishing agent, a cutting pawl 13 can be introduced to separate the fusible conductors 10.

When the bridge igniter 14 is activated, the cutting blade 13 is accelerated in the direction of the fusible conductor 10 and cuts through it.

In the path of movement of the cutting blade 13, a stop area can be provided in the area free of extinguishing agent. This stop area serves to dampen the impact and thus protect the housing wall and the blade. In addition, this area can be used to constrict a gap-like arc. The stop area can be implemented, for example, by a soft or elastic or porous plastic with or without gas release. Alternatively, damping is also possible in a tapering, gap-like area made of insulation material.

The bridge igniter 14 is activated via control lines 15, which are connected to the control 2 (see Fig. 1 ) are directly connectable.

The bridge igniter 14 is located in a housing 16, the housing 16 having a piston 17 which is driven by the bridge igniter 14 and which is connected to a separating element 13.

The area 12 free of extinguishing agent is designed as a channel sealed off from the extinguishing agent 11. The channel has side walls 18 which can also serve to guide the separating element 13.

the Fig. 3 shows an example of the time / current characteristic of an arrangement according to the invention.

For the sake of clarity, the characteristic curves are shown in simplified form only in the time range from approx. 4 ms to 10 s. In addition, the basic course in the time range up to approx. 4 ms was shown.

The adiabatic heating of fusible conductors of the gG fuses can be up to> 5 ms depending on the design of the fusible conductor. The passive fusible conductor of fuse A has, for example, a nominal current of approx. 315 A. Fuse B has a significantly lower nominal current of 100 A, but with almost the same adiabatic melting integral (l ² t value).

On the basis of this value, the pulse current carrying capacity, which is important for use in combination with an overvoltage protection device, for example, is comparable for both fuses. In order to achieve such a characteristic, the fusible conductor B must be designed accordingly or additionally aged.

In the adiabatic time range, the behavior of the proposed protective device is determined by the passive melting behavior of the fuse element of the fuse.

With smaller currents and theoretically longer passive melting times of the respective fuse A or B, the time until the active interruption of the fuse element can be limited as desired, for example from 10 ms to the passive melting time. The time / current characteristic curve can thus be designed as desired below the passive time / current characteristic curve of the fuses. This means that it is also possible to set maximum current flow durations and maximum current flow levels over a wide range. The exemplary range with variable The characteristic curve is limited by the dashed lines below the passive characteristic curves of fusible conductors A and B. This enables good adaptation to various protection tasks.

the Fig. 4 shows a fusible conductor 1A for a capsule fuse with constrictions 2A, which are designed to be longer than known electrical constrictions in order to achieve short melting times with small overcurrents. This leads to an advantageous reduction in the rated current of the fuse. The length of the constrictions corresponds approximately to the distance of the unmediated cross section of the fusible conductor 1A between the constrictions. Between the bottlenecks there is an additional bottleneck 3A for cutting the fusible conductor with a lower degree of modulation than the bottlenecks 2A.

In order to achieve optimal extinguishing properties with a simple quartz sand filling as extinguishing agent, it is advantageous to divide the fusible conductor into several fusible conductors in the case of high impulse currents to be controlled and the associated high metal content. Two fusible conductors of the same design are advantageous for the requirements that are relevant according to the invention.

In principle, the size, the geometry of the fuse housing, the number of fusible conductors, etc. can be varied as required. In addition to a straight fusible conductor guide and two-sided connection to opposite end faces, the connections A and B can of course also be on one side of the housing 6A according to FIG Fig. 5 lie.

In addition to housings made of insulating material, electrically conductive housings with one or two insulated entries for the fusible conductor (s) can also be implemented.

The fusible conductor design can use strips, wires, tubes or the like.

The routing of the fusible conductors and the positioning of the connections must be designed in such a way that the forces, the current levels and, in particular, the protection level of the overall arrangement are maintained in the event of a load with transient pulses. The inductive voltage drop on the fuse arrangement should be <300 V, if possible <200 V for loads greater than 25 kA restrict. In order to reduce the inductance, there is the possibility of designing the fusible conductor guide in a bifilar manner.

Fig. 6 shows a basic arrangement of two fusible conductors 1A with two opposing blades 4A each with an actuator (not shown for simplicity).

The housing serves at the same time as connection A. The further connection B is led out of the housing 6A in an insulated manner. The coaxial arrangement reduces the inductive voltage drop.

Fig. 7 represents a sub-area of the arrangement accordingly Fig. 2 after a separation without the effect of an arc.

In the Fig. 7 the lateral folding of the fusible conductor areas 12A between the blade 4A and the insulation plates can be seen. Due to the tight guidance of these parts, with their corresponding design, the clamping of the parts can also be used to brake the blade 4A and to form a gap.

the Figure 8a shows an arrangement in which the fusible conductors are cut simultaneously and transversely. the Figure 8b shows a simultaneous cutting of the fusible link with vertical alignment to the fusible link. According to Figure 8a the actuator 5a and the cutting blade are integrated directly into the fuse housing to save space.

In Fig. 9 shows a cutting element with two offset blades 4A in cross section, which enables the cutting of two fusible conductors 1A with a short stroke.

According to Fig. 10 a blade 4A or an actuator 5A is used in each case for cutting a fusible conductor 1A. This enables short stroke paths, counter-rotating movement of the blades and, with an appropriate design, partial gap formation directly between the blades 4A, if no additional isolation path with or without extinguishing function or an area with extinguishing agent is provided.

In Fig. 11 a cutting element with two blades 4A and a rotary movement is shown, which can be forced by a corresponding guide and with only one actuator. The blade 4A can in each case be guided in one part in such a way that a good gap formation is possible.

the Fig. 12 shows an embodiment in which a further fuse fusible conductor 13A, which can also be designed in the form of a wire, for example, is not interrupted by the separating device.

The wire can be contacted at the main connections or directly or indirectly at the main fusible conductors.

The wire is preferably surrounded with an extinguishing medium 14A. If the main fusible conductor is interrupted, the current commutates on the wire, which means that arcing in the cutting area can be largely avoided and a high dielectric strength can be achieved after complete separation.

The interruption takes place through a further fusible conductor, which has a very low nominal current strength, in particular below the nominal current strength of the network.

The wire-shaped fusible conductor 13A, for example, can be interrupted with the same cutting edge with a time delay, if necessary, directly or indirectly, in order to enable a current to pass through at 0 A. An indirect interruption is possible in the event of a mechanical displacement or destruction of a carrier on or by the wire. As an alternative to a wire, it is possible to use a fuse element on a carrier 15A accordingly Fig. 13 to execute. Moving an SMD fuse is also feasible.

With further modifications, the explained basic arrangement is suitable for interrupting high short-circuit currents.

The cutting or separating arrangement according to the invention can be located parallel to a horn spark gap 16A, which is short-circuited, for example, with a safety wire 17A of low nominal current strength. When the main fusible conductor is cut, the current commutates on the fuse wire 17A, which ignites the horn spark gap 16A, which in turn extinguishes the current in a quenching chamber 18A, limiting the current.

Such an arrangement is in the Fig. 14 shown as an example.

The requirements with regard to current commutation and the risk of reignition are lower here than with a parallel connection to a fuse with a lower rated current. Ignition of one is also possible Arc directly below the inlet area or directly in an arc chamber. In this case, the requirement with regard to current commutation and re-ignition is already higher than with the classic horn spark gap, but lower than with a parallel fuse of a nominal current strength. In such arrangements, the areas filled with extinguishing agent adjacent to the cutting device can be dispensed with, as a result of which the impedance and the space requirement in the main path are reduced.

In a further embodiment, the cutting device 4A can be located directly in the ignition area of a horn spark gap 16A. The horn spark gap 16A is short-circuited by a securing tape 1A, if necessary with a bottleneck or a defined I ² t value, and is located directly in the main path.

The securing band can be guided outside the cutting area between the diverging electrodes.

The cutting or separating blade is designed in such a way that the arc that occurs when the strip is interrupted is moved in the direction of the quenching chamber and an insulation gap in the horn spark gap according to the desired dielectric strength Fig. 15 arises.

For this purpose, the blade is made at least predominantly from insulation material or is gripped or embedded in insulation material.

After the fusible conductor has been separated, the blade is continued for several millimeters so that the distance between the cut remains of the fusible conductor is greater than 3 mm, but preferably more than 5 mm.

The blade can also be guided laterally next to the diverging electrodes of the horn spark gap in grooves 19A made of insulating material, as a result of which a lateral arcing is avoided.

In addition to activation by the actuator 5A, provision can also be made for the fusible conductor to be thermally separated or moved out of the area between the two electrodes in such a way that a separating distance is created. The blade can also be provided with a mechanical preload, which also allows it to penetrate into the area of the diverging electrodes allowed without activating the actuator. Such embodiments are known from the field of disconnection devices, inter alia, for varistors.

The arrangements and embodiments explained can also be actuated with other internal or external actuators.

Arrangements with spring accumulators are also possible here.

Fig. 16 shows an arrangement with an actuator 5A with a short but variable stroke path. Piezoceramics or the like, for example, can be used here as the actuator.

In this case, the fusible conductor 1A is guided transversely in two insulation parts 20A, which are designed like punch. By moving the actuator, it is possible to carry out a defined modulation of the narrow point 3A of the fusible conductor even after installation and thus to change the characteristic of the fuse as required. A complete severing of the fusible conductor is also possible with a corresponding level of the signal to the actuator 5A.

If there are several fusible conductors, the severing and embossing of the constriction can be carried out by several actuators according to the number of fusible conductors or for several constrictions per fusible conductor. This makes it possible to modify fuses of the same construction for different applications after they have been manufactured. The stamped or embossed parts are preferably made of a material that supports the arc extinguishing, for example ceramic, polymer or the like. In the case of very fine, granular extinguishing agents, the punching area can also be sealed off from the extinguishing agent area by insulation plates 9A. In the case of thinner fusible conductors 1A, this separation is not absolutely necessary if the extinguishing agent has a corresponding grain size.

The activation of the fuse according to the invention depends on the actuators selected. For example, shape memory alloys or bridge detonators can be activated via a current. The electricity can be obtained, for example, from the connected network or from a separate energy store. In the case of bridge igniters, the small amount of energy required can also be provided galvanically separated by a transformer.

The degree of triggering for the activation of the fuse is designed in such a way that activation using several criteria is possible. Here, actively controllable switches can be used which have internal evaluation electronics or an external control option. In the simplest case, these switches can also be means which react directly to physical variables and which are provided in parallel with the controllable switch. Such switches can react to limit values or changes in temperature, pressure, current, voltage, optical signals, volume or the like or combinations thereof. Electronic, mechanical, voltage-switching, but also impedance-changing components can also be used as switches.

the Fig. 17 Another embodiment of the invention shows a fusible conductor 1B with usual constrictions 2B in the form of elongated recesses. An area with an undiminished cross section 3B is provided between these usual recesses, which in this case is similar in length to the recesses. An exemplary embodiment of an additional mechanical constriction 4B is formed within this area. This constriction 4B is implemented as a diamond-shaped recess with a short overall length.

Such a design has the advantage, especially when using the fuse according to the invention in the shunt branch, that in the event of a short-circuit load, no additional arc voltage is caused by a simultaneous arc formation with regard to the additional and known bottlenecks, whereby the voltage load of the consumer to be protected remains controllable.

The short bottleneck can be realized without any significant lengthening of the fusible conductor and without a relevant reduction in the material of the fusible conductor, which is necessary for a controlled arc lengthening. Due to the design explained, the constriction also does not lead to additional pressure or temperature stress on the fuse housing.

The relatively central position of the additional mechanical constriction surrounded by extinguishing medium, for example common quartz sand, leads to a comparatively high extinguishing capacity when the constriction is destroyed, since, in addition to good cooling and mechanical elongation, there is also an extension on both sides of the arc can take place quite quickly as a result of arc erosion into the area of the normal bottlenecks.

In principle, the mechanical tension bottleneck can also be provided by the actuator at other positions of the fusible conductor, for example immediately in front of the first electrical bottleneck in the pulling direction. It should be noted, however, that the free length of the fusible link in the area filled with the extinguishing agent may have to be extended in accordance with the desired actively switchable short-circuit currents. The mechanical constriction therefore does not necessarily have to be located in the center of the fusible link.

The above allows the fuse to be activated even with the separation of just one narrow point at high currents with virtual melting times of <10 ms. Thus, the fuse according to the invention can interrupt practically in the current-free state, with small currents far below the nominal current strength and even high fault currents in the kA ampere range after a short time. Almost any time / current characteristic curve can also be implemented, depending on the requirements.

As an alternative to a free fusible lead and a tensile effect on the entire fusible conductor, strain relief on the fusible conductor or the partial fixation of the fusible conductor in the so-called "stone sand" are also possible. This means that the force can be directed specifically to a single bottleneck.

When using coarse or angular extinguishing sand, it can make sense to provide the usual, normal electrical constrictions between the actuator and the mechanical tension constriction, for example with an insulating film, so that the additional friction is reduced.

the Fig. 18 shows a fusible conductor 1B for a capsule fuse with constrictions 2B, which are designed to be longer than usual constrictions in order to achieve short melting times with small overcurrents. The distance between the undiminished cross section 3B of the fusible conductor between the constrictions, however, in this case corresponds at least to the length of the constriction.

This already leads to an advantageous reduction in the rated current of the fuse. In the case of active securing, the elongation of these bottlenecks increases with a tensile load and the requirements for the mechanical, additional ones Narrow point rise. In order to achieve optimal extinguishing properties with a simple quartz sand filling, it is advantageous to divide the fusible conductor into several fusible conductors in the case of high pulse currents to be controlled and the associated high metal content. Two identically designed fusible conductors are advantageous here.

Figure 19 shows an embodiment in which the further mechanical constriction 4B according to the invention is introduced between the normal constrictions 2B. With a length of ideally a few 10 µm, this constriction is unsuitable as a usual constriction and does not support its passive function in the event of short-circuit switch-offs. Despite a smaller cross-section, the constriction does not respond to these loads, which means that no additional arc voltage is generated. The function is therefore limited to the active control of the fuse.

The length of the bottleneck is at least a factor of 4, but ideally greater than 10 less than the length of the usual, known bottlenecks.

In the case of a mechanical constriction with a maximum length of, for example, 500 μm, the usual known constrictions are longer than 4 mm. Better ratios result with a length of <150 µm compared to lengths of> 2 mm with conventional, known constrictions.

The cross section of the constriction according to the invention is at least a factor of 20% smaller, ideally more than 50% smaller than the normal constriction. The usual, normal bottlenecks have a degree of modulation of approx. 2 in relation to the undiminished cross-section. This relatively low degree of modulation makes sense because of the small amount of metal required for small sizes.

For small fuse designs, due to the limitation of the ratio of fuse element material and extinguishing medium for the fuse element, copper or copper alloys are usually used.

The required tensile force of the constrictions to tear them is at most 80%, but ideally <60% based on the forces that lead to the tearing of normal constrictions.

Until the mechanical constriction is torn, the total fusible conductor in the case of soft copper is at most stretched by 3 mm, preferably less than 1 mm. This corresponds to <5% of the total length of the fuse element.

In the case of copper, an elongation of approx. 40% is required to tear the mechanical constriction with a diamond-shaped design. Even with an individual length of 4 mm, the usual constrictions only expand by <8% in total, the undiminished cross-section of the fusible conductor only expands by a value of <1%. In the case of shorter bottlenecks, the expansion can be restricted even more to the mechanical bottleneck despite the effect of the force on the entire length of the fusible conductor. This allows complete integration into a customary, small fuse size, even with unfavorable material.

The possible stroke path within the fuse is limited to at least twice the path that is required to safely tear the mechanical bottleneck and is designed accordingly. However, the path can also be made longer to achieve sufficient dielectric strength.

By limiting the tensile force to only one area of the fusible conductor with the mechanical constriction, the expansion can be further reduced.

the Figures 20a to 20c show design variants of the additional, mechanical constriction.

In Figure 20a a fusible conductor 1B with four normal constrictions 2B with a degree of modulation of 2 is shown. The length of the bottlenecks is 4 mm, which means that the rated current can be reduced to approx. 160 A. The heating of the constrictions with a load of 25 kA 10/350 µs is approx. 700 ° C, whereby there is still sufficient aging stability. The mechanical predetermined breaking point 4B is dimensioned in such a way that it can be produced with the simplest of punching processes and at the same time with the normal, known constrictions. The length is, for example, 0.5 mm. However, the cross-section of the transversely arranged elongated holes is reduced by 20% compared to the normal narrow points. The temperature of this bottleneck is at the same level as the temperature of the other bottlenecks in the case of pulse loads.

In Figure 20b shows a bottleneck 4B of the same overall length, but with a diamond-shaped geometry. The diamonds significantly shorten the area of the minimum remaining cross-section compared to the total length. The remaining cross-section can be reduced to 60% based on the remaining constrictions at the same temperature. The reduction in the force required to destroy the mechanical constriction is in the same range. The design of such bottlenecks or similar bottlenecks is limited exclusively by the technology and the costs for reproducible production.

According to Figure 20c a constriction design 4B can take place, which is limited to a thickness modulation. In this illustration, the fusible conductor 1B is not shown in a plan view of the width of the fusible conductor. The view relates to the thickness of the fuse element 1B in side view. With a uniform, bilateral modulation over an overall small bottleneck length 4B, for example of only 50-150 µm, the cross-section and the required force can be reduced to approx. 40% compared to the normal bottlenecks with the same heating in the case of impulse currents. In the illustrated Figure 20c the remaining thickness in the narrow point area, which is uniform over the width of the fusible conductor, is only about a third of the total length of the narrow point.

The variant according to Figure 20c discloses a design which allows a sufficiently uniform current density distribution in the case of impulse currents with very strong cooling of the constriction. The heating of the constriction in the case of impulse currents can thus be significantly below normal constrictions, despite the smaller residual cross-section and sufficient force reduction, if this is advantageous for the overall function. The assumed same temperature increase for impulse currents, in which the response of the bottlenecks is to be avoided, leads to higher temperatures at the normal bottlenecks in the case of mains-frequency currents, which means that arcing can be avoided with passive behavior at the drawing bottleneck. With a load with a short-circuit current of approx. 4 kA and a virtual melting time of approx. 10 ms, the temperature at the pulling or pulling point is only 211 ° C (T0 = 22 ° C) when the melting temperature is reached at the usual, known constrictions .

In Figure 21a and b an exemplary structure of a NH fuse in capsule design is shown in detail. the Figure 21a shows the normal state and the Figure 21b the triggered state.

The fuse preferably has an insulating housing 5B, two main fusible conductors 1B, a metallic end cap 6B on both sides for connection, on which the fusible conductors 1B are contacted.

With a small size, the fuse has a design for at least one or two control connections 8B for activating the igniter 7B. The control connections 8B can be led out axially but also radially out of the housing or the end caps of the fuse. Wireless activation is also possible for larger versions.

The ignition device, designed for example as a bridge igniter 7B, is located in a small cavity 9B surrounded by a projectile 10B, which is guided in a type of piston 11B. In this case, two fusible conductors 1B, each with a central mechanical constriction 4B, are firmly connected to the projectile 10B.

The connection can be positive or non-positive, for example by soldering, welding or clamping.

The fusible conductors are preferably clamped under pressure between a conical area of the projectile 10B and a further conical part 12B. When a force is applied to the projectile 10B when the bridge detonator 7B is actuated, the clamping force increases further, so that it is not possible to loosen the clamping connection. If the installation space is small, the parts can be shaped cylindrically and the fusible conductors can be shaped as half-shells.

The fusible conductors are located below the piston 11B in a space 13B filled with extinguishing agent. Quartz sand is the preferred extinguishing agent. Preferably all bottlenecks in the fusible link are surrounded by the extinguishing agent.

The piston 11B is located in an intermediate part 14B which delimits the space with extinguishing agent from a cavity 15B above the projectile 10B.

The intermediate part 14B can consist of an insulating part or also partially or completely of electrically conductive material.

The intermediate part 14B can be designed cup-shaped and rest on the housing part 5B with an edge.

Between the intermediate part 14B and the end cap 6B, a substantially ring-shaped part 16B can be provided, on which the fusible conductors 1B are contacted by the end cap 6B.

A current flow between the fusible conductors 1B and the end cap 6B via the intermediate part 14B can, if necessary, be prevented by a suitable choice of material or an insulation layer.

The end cap 6B and the parts 5B and 14B as well as 16B are designed in such a way that the fuse is finally closed by pressing on the end cap 6B.

In the area of the part 14B below the piston 11B, there is an effective seal with respect to the extinguishing agent, which does not allow the extinguishing medium to detach even when the fusible conductors are moving.

The two fusible conductors 1B are implemented above the piston 11B and the projectile 10B in the extinguishing agent-free space 15B with areas angled relative to the axis.

When the projectile 10B moves into the space 15B free of extinguishing agent, the sealing guidance between the projectile 10B and the piston 11B is only released after the fusible conductor has been severed at the mechanical constriction 4B.

Shows the disconnected state Figure 21b .

The angled areas of the fusible link are bent in the opposite direction with minimal effort when moving in the extinguishing agent-free space. Bending the straps does not require pressure equalization in a small volume without an extinguishing agent, as the air is not displaced against an enclosed space. It is advantageous in this embodiment that no additional interruption or contacting of the fusible conductor or conductors is necessary for the contacting of the fusible conductor and the extension of the isolating distance.

The fusible strips used as an example can be guided through the fuse with very low impedance and without additional deflections or movements over a short distance. Overall, a very low-resistance fusible conductor material is used despite the relatively high elongation at break of such materials. The impedance of the arrangement is low, so that the ohmic and inductive voltage drop across the fuse and thus the influence on the protection level of the arrangement is low even with a high rate of current steepness and high currents. With 25 kA 8/20 µs pulses the voltage drop is <300 V, preferably less than 200 V.

As an alternative to the arrangement explained, the projectile can also be connected directly or indirectly to the connection caps with transverse connecting tape, a flexible line, a multiple contact system or the like. In this case, the fusible conductor area ends at the projectile.

When using shape memory alloys or volume-changing materials, a structure similar to that described above can be used, whereby the seal between the projectile and the piston can be dispensed with. In the case of the use of shape memory alloys, if the tensile force is used, an embodiment according to FIGS Figure 22a and b possible.

In the Figure 22a and 22b only one segment of the structure is shown in detail for the purpose of explanation. The position of the segment within the sketched fuse 17B in capsule design is indicated by dashed areas.

For the sake of simplicity, the functionality is shown in accordance with the Figure 22a and 22b only explained on the basis of a fuse element 1B. The fusible conductor 1B has a substantially U-shaped section 18B. The fusible conductor itself is passed through two plate-like bushings 19B and 20B.

The implementation is implemented, for example, as a first fixed plate 19 and is located in the area of the U-shaped section of the fusible conductor. The second plate 20B is movable and is located in the transition area to an axial fusible conductor area. Between the two plates, the fusible conductor runs at an acute angle to the second plate 20B.

After the U-shaped area and the second plate 20B as well as a further plate 21B for sealing off the extinguishing agent, there is the mechanical, additional bottleneck 4B. There is no extinguishing agent or bottleneck in the fuse between the two plates.

When a tensile force is applied to the second plate 20B in the direction of the U-shaped deflection, the tensile force acts directly as a tearing force on the mechanical constriction 4B. The tensile force can be implemented via a shape memory element 22B fastened directly or indirectly to the second plate, for example through its direct or indirect heating.

The plates 21B and 19B seal off the U-shaped area of the fusible conductor with the movable plate 20B from the ingress of extinguishing agent.

The areas 23B and 24B are filled with extinguishing agent.

The majority of the usual constrictions of the fusible conductor are located in the region 23B. The mechanical bottleneck 4B is located in the area 24B. the Figure 22a shows the arrangement described in normal operation and Figure 22b the status after the bottleneck interruption.

When the plate 19B is pulled, it presses on the area of the U-shaped fusible conductor guide. The fusible conductor is clamped between the plates and a further movement leads to an immediate loading of the mechanical constriction with a sufficient tensile force, which overloads the mechanical constriction 4B.

The activation of the fuse depends on the selected actuators. For example, the activation can take place by means of shape memory alloys or on the bridge igniter by means of a current. The electricity can be obtained from the adjacent network, but also from a separate storage facility. Here, too, a bridge igniter has the option of providing the required energy, galvanically separated, by means of a transformer.

The trigger circuit for activation is designed in such a way that it can take place with the aid of several criteria. As already explained, actively controllable switches or switches that react directly to physical variables can be used.

A tensile force can also be applied to the fusible link, which is located in the extinguishing agent to the quartz sand, with permanent spring force. At a Embodiment according to Fig. 23 a tensile force is now not applied to a mechanical bottleneck, but rather a tensile force at a soldering point, which can be released within 1 ms, for example by a reaction film (exothermic reaction). The extension requires a stroke which includes the length of the soldering path and the required isolating distance.

According to Fig. 23 the fuse has a housing 5B with connection caps 6B. The fusible conductor 1B is divided into two areas which are connected to one another by a solder 25B. A reaction film 26B with exothermic heat generation is arranged in the region of the connection. The reaction of the foil can be triggered by an auxiliary fuse or a spark generator 27B. The control takes place here via one or two connection lines 8B. The connection point is located in the area of the fuse with extinguishing agent 13B. This area is sealed off from an area 15B free of extinguishing agent by a leadthrough 28B. In this area there is a spring 29B which mechanically pretensions the fusible conductor 1B. After the soldered connection 25B has been loosened, the fusible conductor 1B is kinked in the area 15B (dashed position) and pulled through the area 15B, so that there is a sufficiently long separating distance between the two remaining fusible conductor parts.

Claims (15)

Triggerable fuse for low-voltage applications to protect devices that can be connected to a supply network, in particular overvoltage protection devices, consisting of at least one fusible link located between two contacts and arranged in a housing as well as with a trigger device for the controlled disconnection of the fusible link in the event of malfunctions or overload conditions of the respectively connected device, whereby an extinguishing agent is introduced in the housing, characterized in that the at least one fusible link has a large number of known electrical constrictions which are designed for the nominal load of the respective fuse, at least one further, additional geometric constriction being provided which is subject to tensile stress Depending on the trigger unit can be separated by tearing. Triggerable fuse according to Claim 1, characterized in that the at least one geometric constriction has a residual cross section which is smaller than the residual cross section of the electrical constrictions. Triggerable fuse according to Claim 1 or 2, characterized in that the trigger device controls an actuator. Triggerable fuse according to claim 3, characterized in that the actuator consists of a piston, the movement of which is triggered by a bridge detonator, in particular wherein the bridge detonator is located in a cavity surrounded by a projectile which is guided in the piston, preferably two on the projectile Fusible conductors are each firmly connected to a central, geometric constriction. Triggerable fuse according to Claim 3 or 4, characterized in that the actuator causes a defined extension of the interrupted fusible conductor, so that the resulting overall isolating distance achieves a dielectric strength of at least 2.5 kV. Triggerable fuse according to one of the preceding claims, characterized in that the fusible link has several has conventional electrical bottlenecks in series, the number of which corresponds to the usual design for the corresponding rated voltage of the fuse. Triggerable fuse according to one of the preceding claims, characterized in that the at least one further, additional geometric constriction is provided between the electrical constrictions. Triggerable fuse according to one of the preceding claims, characterized in that the triggerable fuse is based on a defined tearing of the at least one further, additional geometric constriction of the fusible conductor in the extinguishing agent after activation of a trigger. Triggerable fuse according to one of the preceding claims, characterized in that the at least one further, additional geometrical constriction is a geometrical predetermined breaking point, in particular wherein the at least one further, additional geometrical constriction is a constriction. Triggerable fuse according to one of the preceding claims, characterized in that the at least one further, additional geometric constriction, despite a smaller cross-section with the same current load, does not respond before the electrical constrictions at all current loads, but with a time delay or at higher loads. Triggerable fuse according to one of the preceding claims, characterized in that the melting integral value of the at least one further, additional geometric constriction in the period of transient pulse current loads is equal to or even greater than that of the electrical constriction, in particular wherein the at least one further, additional geometric constriction has a residual cross-section which is significantly less than that of the electrical bottlenecks. Triggerable fuse according to one of the preceding claims, characterized in that the mechanical strength of the at least one further, additional geometric constriction compared to the The direction of force of the actuator is significantly smaller than the mechanical strength of the electrical bottlenecks. Triggerable fuse according to one of the preceding claims, characterized in that the at least one further, additional geometric constriction is made significantly smaller in terms of its dimensions than the electrical constrictions. Triggerable fuse according to one of the preceding claims, characterized in that the length of the at least one further, additional geometric constriction is made smaller by at least a factor of 4, in particular greater than a factor of 10, than the length of the electrical constriction. Triggerable fuse according to one of the preceding claims, characterized in that the at least one further, additional geometric constriction is unsuitable as an electrical constriction.

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